(1) Field of the Invention
The present invention relates to a flame-retardant liquid crystal polyester composition having superior flame retardancy, especially high resistance to fall out of granules during of combustion, and providing a shaped article having good heat resistance, mechanical properties, and appearance.
(2) Description of the Prior Art
The demand for an enhancement of the performance of plastics has increased, and many polymers having good performances have been developed and marketed. Among these polymers, optically anisotropic liquid crystal polymers characterized by a parallel configuration of molecule chains have attracted attention, due to their superior flowability and mechanical properties, and the application of these polymers as machine parts, electric and electronic parts, and the like is widening.
In addition to a balance among general chemical and physical properties, a high degree of safety against a flame, i.e., a high flame retardancy, is urgently required for these industrial materials.
It is known, in general, that a liquid crystal polymer has good combustion resistance and when the polymer is directly exposed to a flame, foaming spontaneously occurs and a carbonized layer is formed.
Nevertheless, it was found that since a liquid crystal polyester formed by copolymerizing a polyester derived from an alkylene glycol and a dicarboxylic acid with an acyloxy aromatic carboxylic acid (for example, a polymer disclosed in Japanese Examined Patent Publication No. 56-18016) contains an aliphatic component, and thus the flame retardancy of a thin (1/32") shaped article of this polymer is poor as compared with the flame retardancy of a wholly aromatic polyester (for example, Vectra A-130 supplied by Polyplastics Co. Ltd.).
Accordingly, the inventors incorporated various flame retardants in the polymer disclosed in Japanese Examined Patent Publication No. 56-18016, and found that, although the flame retardancy of a thin shaped article having a thickness of e.g. 1/32 inch is improved, a shaped article having good heat resistance, mechanical properties, and appearance cannot be obtained.